Detonative cleaning apparatus nozzle

ABSTRACT

An apparatus directs gas from an upstream conduit through a vessel wall for cleaning surfaces within the vessel. A mounting flange couples the apparatus to the upstream conduit delivering the gas. The flange has first and second faces, an inboard surface bounding a central aperture, an outboard perimeter, and an array of bolt holes between the first and second faces. A conduit extends downstream from the flange and has inner and outer walls along at least a portion of a length and a space between the inner and outer walls for carrying a cooling fluid. The apparatus has a cooling fluid inlet and a cooling fluid outlet.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to industrial equipment. More particularly, theinvention relates to the detonative cleaning of industrial equipment.

(2) Description of the Related Art

Surface fouling is a major problem in industrial equipment. Suchequipment includes furnaces (coal, oil, waste, etc.), boilers,gasifiers, reactors, heat exchangers, and the like. Typically theequipment involves a vessel containing internal heat transfer surfacesthat are subjected to fouling by accumulating particulate such as soot,ash, minerals and other products and byproducts of combustion, moreintegrated buildup such as slag and/or fouling, and the like. Suchparticulate build-up may progressively interfere with plant operation,reducing efficiency and throughput and potentially causing damage.Cleaning of the equipment is therefore highly desirable and is attendedby a number of relevant considerations. Often direct access to thefouled surfaces is difficult. Additionally, to maintain revenue it isdesirable to minimize industrial equipment downtime and related costsassociated with cleaning. A variety of technologies have been proposed.By way of example, various technologies have been proposed in U.S. Pat.Nos. 5,494,004 and 6,438,191 and U.S. patent application publication2002/0112638. Additional technology is disclosed in Huque, Z.Experimental Investigation of Slag Removal Using Pulse Detonation WaveTechnique, DOE/HBCU/OMI Annual Symposium, Miami, Fla. Mar. 16-18, 1999.Particular blast wave techniques are described by Hanjalić and Smajevićin their publications: Hanjalić, K. and Smajević, I., Further ExperienceUsing Detonation Waves for Cleaning Boiler Heating Surfaces,International Journal of Energy Research Vol. 17, 583-595 (1993) andHanjalić, K. and Smajević, I., Detonation-Wave Technique for On-loadDeposit Removal from Surfaces Exposed to Fouling: Parts I and II,Journal of Engineering for Gas Turbines and Power, Transactions of theASME, Vol. 1, 116 223-236, January 1994. Such systems are also discussedin Yugoslav patent publications P 1756/88 and P 1728/88. Such systemsare often identified as “soot blowers” after an exemplary applicationfor the technology.

Nevertheless, there remain opportunities for further improvement in thefield.

SUMMARY OF THE INVENTION

One aspect of the invention involves an apparatus for directing gas froman upstream conduit through a vessel wall for cleaning surfaces withinthe vessel. A mounting flange couples the apparatus to the upstreamconduit delivering the gas and has first and second faces, an inboardsurface bounding a central aperture, an outboard perimeter, and an arrayof bolt holes extending between the first and second faces. A conduitextends downstream from the flange and has inner and outer walls alongat least a portion of a length. A space between the inner and outerwalls carries a cooling fluid. There is a cooling fluid inlet and acooling fluid outlet.

In various implementations, the space may extend from an upstream endoutside the vessel wall at least partially downstream within the wall.The cooling fluid outlet may be along the conduit and the cooling fluidinlet may be along the flange. The inner and outer walls may each have adownstream rim. The cooling fluid outlet may be between the inner andouter walls. The inner wall may essentially be formed by a first tubularpiece extending from an upstream rim to a downstream rim and havinginterior and exterior surfaces. Along an upstream portion, the interiorsurface may provide the flange inboard surface. The apparatus may becombined with the vessel. The vessel may be a furnace having a furnacewall separating a furnace exterior from a furnace interior and having awall aperture. The combination may include a detonative source of thegas. The flange may be upstream of an exterior surface of the furnacewall. The conduit may extend through the furnace wall to protrudedownstream of an interior surface of the furnace wall.

Another aspect of the invention involves a soot blower nozzle. Meansmount the nozzle to an upstream soot blower gas conduit. A surfaceguides gas from the soot blower gas conduit into the interior of thevessel. Means cool the nozzle.

Another aspect of the invention involves a method for operating anapparatus for cleaning interior surfaces within a vessel having a vesselwall. A combustion pulse is caused in a combustion conduit. Combustiongases are directed along the combustion conduit through the vessel wallto be ejected from an outlet of the combustion conduit. A cooling gas ispassed along a portion of the combustion conduit exposed to heat fromthe vessel.

In various implementations, the passing may be essentially continuousbetween a number of the combustion pulses. The passing may includepassing the cooling fluid along a path at least partially surrounding aportion of the combustion gas flowpath. The passing may include passingthe cooling fluid along a path into the vessel interior.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of an industrial furnace associated with several sootblowers positioned to clean a level of the furnace.

FIG. 2 is a side view of one of the blowers of FIG. 1.

FIG. 3 is a partially cut-away side view of an upstream end of theblower of FIG. 2.

FIG. 4 is a longitudinal sectional view of a main combustor segment ofthe soot blower of FIG. 2.

FIG. 5 is an end view of the segment of FIG. 4.

FIG. 6 is a side view of an alternate discharge end portion of acombustion tube assembly.

FIG. 7 is a view of an air curtain flange of the assembly of FIG. 6.

FIG. 8 is a downstream end view of the flange of FIG. 7.

FIG. 9 is a downstream end view of a thermal isolation flange assembly.

FIG. 10 is an exploded view of the assembly of FIG. 9.

FIG. 11 is a view of a nozzle assembly.

FIG. 12 is a downstream end view of a nozzle assembly of FIG. 11.

FIG. 13 is a longitudinal sectional view of the nozzle assembly of FIG.12, taken along line 13-13.

FIG. 14 is an enlarged view of a flange portion of the nozzle assemblyof FIG. 13.

FIG. 15 is a partial longitudinal sectional view of a downstream endportion of the nozzle assembly of FIG. 11.

FIG. 16 is a partial longitudinal sectional view of an alternate aircurtain flange.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 shows a furnace 20 having an exemplary three associated sootblowers 22. In the illustrated embodiment, the furnace vessel is formedas a right parallelepiped and the soot blowers are all associated with asingle common wall 24 of the vessel and are positioned at like heightalong the wall. Other configurations are possible (e.g., a single sootblower, one or more soot blowers on each of multiple levels, and thelike).

Each soot blower 22 includes an elongate combustion conduit 26 extendingfrom an upstream distal end 28 away from the furnace wall 24 to adownstream proximal end 30 closely associated with the wall 24.Optionally, however, the end 30 may be well within the furnace. Inoperation of each soot blower, combustion of a fuel/oxidizer mixturewithin the conduit 26 is initiated proximate the upstream end (e.g.,within an upstreammost 10% of a conduit length) to produce a detonationwave which is expelled from the downstream end as a shockwave along withassociated combustion gases for cleaning surfaces within the interiorvolume of the furnace. Each soot blower may be associated with afuel/oxidizer source 32. Such source or one or more components thereofmay be shared amongst the various soot blowers. An exemplary sourceincludes a liquified or compressed gaseous fuel cylinder 34 and anoxygen cylinder 36 in respective containment structures 38 and 40. Inthe exemplary embodiment, the oxidizer is a first oxidizer such asessentially pure oxygen. A second oxidizer may be in the form of shopair delivered from a central air source 42. In the exemplary embodiment,air is stored in an air accumulator 44. Fuel, expanded from that in thecylinder 34 is generally stored in a fuel accumulator 46. Each exemplarysource 32 is coupled to the associated conduit 26 by appropriateplumbing below. Similarly, each soot blower includes a spark box 50 forinitiating combustion of the fuel oxidizer mixture and which, along withthe source 32, is controlled by a control and monitoring system (notshown). FIG. 1 further shows the wall 24 as including a number of portsfor inspection and/or measurement. Exemplary ports include an opticalmonitoring port 54 and a temperature monitoring port 56 associated witheach soot blower 22 for respectively receiving an infrared and/orvisible light video camera and thermocouple probe for viewing thesurfaces to be cleaned and monitoring internal temperatures. Otherprobes/monitoring/sampling may be utilized, including pressuremonitoring, composition sampling, and the like.

FIG. 2 shows further details of an exemplary soot blower 22. Theexemplary detonation conduit 26 is formed with a main body portionformed by a series of doubly flanged conduit sections or segments 60arrayed from upstream to downstream and a downstream nozzle conduitsection or segment 62 having a downstream portion 64 extending throughan aperture 66 in the wall and ending in the downstream end or outlet 30exposed to the furnace interior 68. The term nozzle is used broadly anddoes not require the presence of any aerodynamic contraction, expansion,or combination thereof. Exemplary conduit segment material is metallic(e.g., stainless steel). The outlet 30 may be located further within thefurnace if appropriate support and cooling are provided. FIG. 2 furthershows furnace interior tube bundles 70, the exterior surfaces of whichare subject to fouling. In the exemplary embodiment, each of the conduitsegments 60 is supported on an associated trolley 72, the wheels ofwhich engage a track system 74 along the facility floor 76. Theexemplary track system includes a pair of parallel rails engagingconcave peripheral surfaces of the trolley wheels. The exemplarysegments 60 are of similar length L₁ and are bolted end-to-end byassociated arrays of bolts in the bolt holes of their respectiveflanges. Similarly, the downstream flange of the downstreammost of thesegments 60 is bolted to the upstream flange of the nozzle 62. In theexemplary embodiment, a reaction strap 80 (e.g., cotton orthermally/structurally robust synthetic) in series with one or moremetal coil reaction springs 82 is coupled to this last mated flange pairand connects the combustion conduit to an environmental structure suchas the furnace wall for resiliently absorbing reaction forces associatedwith discharging of the soot blower and ensuring correct placement ofthe combustion conduit for subsequent firings. Optionally, additionaldamping (not shown) may be provided. The reaction strap/springcombination may be formed as a single length or a loop. In the exemplaryembodiment, this combined downstream section has an overall length L₂.Alternative resilient recoil absorbing means may include non-metal ornon-coil springs or rubber or other elastomeric elements advantageouslyat least partially elastically deformed in tension, compression, and/orshear, pneumatic recoil absorbers, and the like.

Extending downstream from the upstream end 28 is a predetonator conduitsection/segment 84 which also may be doubly flanged and has a length L₃.The predetonator conduit segment 84 has a characteristic internalcross-sectional area (transverse to an axis/centerline 500 of theconduit) which is smaller than a characteristic internal cross-sectionalarea (e.g., mean, median, mode, or the like) of the downstream portion(60, 62) of the combustion conduit. In an exemplary embodiment involvingcircular sectioned conduit segments, the predetonator cross-sectionalarea is a characterized by a diameter of between 8 cm and 12 cm whereasthe downstream portion is characterized by a diameter of between 20 cmand 40 cm. Accordingly, exemplary cross-sectional area ratios of thedownstream portion to the predetonator segment are between 1:1 and 10:1,more narrowly, 2:1 and 10:1. An overall length L between ends 28 and 30may be 1-15 m, more narrowly, 5-15 m. In the exemplary embodiment, atransition conduit segment 86 extends between the predetonator segment84 and the upstreammost segment 60. The segment 86 has upstream anddownstream flanges sized to mate with the respective flanges of thesegments 84 and 60 has an interior surface which provides a smoothtransition between the internal cross-sections thereof. The exemplarysegment 86 has a length L₄. An exemplary half angle of divergence of theinterior surface of segment 86 is ≦12°, more narrowly 5-10°.

A fuel/oxidizer charge may be introduced to the detonation conduitinterior in a variety of ways. There may be one or more distinctfuel/oxidizer mixtures. Such mixture(s) may be premixed external to thedetonation conduit, or may be mixed at or subsequent to introduction tothe conduit. FIG. 3 shows the segments 84 and 86 configured for distinctintroduction of two distinct fuel/oxidizer combinations: a predetonatorcombination; and a main combination. In the exemplary embodiment, in anupstream portion of the segment 84, a pair of predetonator fuelinjection conduits 90 are coupled to ports 92 in the segment wall whichdefine fuel injection ports. Similarly, a pair of predetonator oxidizerconduits 94 are coupled to oxidizer inlet ports 96. In the exemplaryembodiment, these ports are in the upstream half of the length of thesegment 84. In the exemplary embodiment, each of the fuel injectionports 92 is paired with an associated one of the oxidizer ports 96 ateven axial position and at an angle (exemplary 90° shown, although otherangles including 180° are possible) to provide opposed jet mixing offuel and oxidizer. Discussed further below, a purge gas conduit 98 issimilarly connected to a purge gas port 100 yet further upstream. An endplate 102 bolted to the upstream flange of the segment 84 seals theupstream end of the combustion conduit and passes through anigniter/initiator 106 (e.g., a spark plug) having an operative end 108in the interior of the segment 84.

In the exemplary embodiment, the main fuel and oxidizer are introducedto the segment 86. In the illustrated embodiment, main fuel is carriedby a number of main fuel conduits 112 and main oxidizer is carried by anumber of main oxidizer conduits 110, each of which has terminalportions concentrically surrounding an associated one of the fuelconduits 112 so as to mix the main fuel and oxidizer at an associatedinlet 114. In exemplary embodiments, the fuels are hydrocarbons. Inparticular exemplary embodiments, both fuels are the same, drawn from asingle fuel source but mixed with distinct oxidizers: essentially pureoxygen for the predetonator mixture; and air for the main mixture.Exemplary fuels useful in such a situation are propane, MAPP gas, ormixtures thereof. Other fuels are possible, including ethylene andliquid fuels (e.g., diesel, kerosene, and jet aviation fuels). Theoxidizers can include mixtures such as air/oxygen mixtures ofappropriate ratios to achieve desired main and/or predetonator chargechemistries. Further, monopropellant fuels having molecularly combinedfuel and oxidizer components may be options.

In operation, at the beginning of a use cycle, the combustion conduit isinitially empty except for the presence of air (or other purge gas). Thepredetonator fuel and oxidizer are then introduced through theassociated ports filling the segment 84 and extending partially into thesegment 86 (e.g., to near the midpoint) and advantageously just beyondthe main fuel/oxidizer ports. The predetonator fuel and oxidizer flowsare then shut off. An exemplary volume filled the predetonator fuel andoxidizer is 1-40%, more narrowly 1-20%, of the combustion conduitvolume. The main fuel and oxidizer are then introduced, to substantiallyfill some fraction (e.g., 20-100%) of the remaining volume of thecombustor conduit. The main fuel and oxidizer flows are then shut off.The prior introduction of predetonator fuel and oxidizer past the mainfuel/oxidizer ports largely eliminates the risk of the formation of anair or other non-combustible slug between the predetonator and maincharges. Such a slug could prevent migration of the combustion frontbetween the two charges.

With the charges introduced, the spark box is triggered to provide aspark discharge of the initiator igniting the predetonator charge. Thepredetonator charge being selected for very fast combustion chemistry,the initial deflagration quickly transitions to a detonation within thesegment 84 and producing a detonation wave. Once such a detonation waveoccurs, it is effective to pass through the main charge which might,otherwise, have sufficiently slow chemistry to not detonate within theconduit of its own accord. The wave passes longitudinally downstream andemerges from the downstream end 30 as a shockwave within the furnaceinterior, impinging upon the surfaces to be cleaned and thermally andmechanically shocking to typically at least loosen the contamination.The wave will be followed by the expulsion of pressurized combustionproducts from the detonation conduit, the expelled products emerging asa jet from the downstream end 30 and further completing the cleaningprocess (e.g., removing the loosened material). After or overlappingsuch venting of combustion products, a purge gas (e.g., air from thesame source providing the main oxidizer and/or nitrogen) is introducedthrough the purge port 100 to drive the final combustion products outand leave the detonation conduit filled with purge gas ready to repeatthe cycle (either immediately or at a subsequent regular interval or ata subsequent irregular interval (which may be manually or automaticallydetermined by the control and monitoring system)). Optionally, abaseline flow of the purge gas may be maintained betweencharge/discharge cycles so as to prevent gas and particulate from thefurnace interior from infiltrating upstream and to assist in cooling ofthe detonation conduit.

In various implementations, internal surface enhancements maysubstantially increase internal surface area beyond that provided by thenominally cylindrical and frustoconical segment interior surfaces. Theenhancement may be effective to assist in the deflagration-to-detonationtransition or in the maintenance of the detonation wave. FIG. 4 showsinternal surface enhancements applied to the interior of one of the mainsegments 60. The exemplary enhancement is nominally a Chin spiral,although other enhancements such as Shchelkin spirals and Smirnovcavities may be utilized. The spiral is formed by a helical member 120.The exemplary member 120 is formed as a circular-sectioned metallicelement (e.g., stainless steel wire) of approximately 8-20 mm insectional diameter. Other sections may alternatively be used. Theexemplary member 120 is held spaced-apart from the segment interiorsurface by a plurality of longitudinal elements 122. The exemplarylongitudinal elements are rods of similar section and material to themember 120 and welded thereto and to the interior surface of theassociated segment 60. Such enhancements may also be utilized to providepredetonation in lieu of or in addition to the foregoing techniquesinvolving different charges and different combustor cross-sections.

The apparatus may be used in a wide variety of applications. By way ofexample, just within a typical coal-fired furnace, the apparatus may beapplied to: the pendants or secondary superheaters, the convective pass(primary superheaters and the economizer bundles); air preheaters;selective catalyst removers (SCR) scrubbers; the baghouse orelectrostatic precipitator; economizer hoppers; ash or otherheat/accumulations whether on heat transfer surfaces or elsewhere, andthe like. Similar possibilities exist within other applicationsincluding oil-fired furnaces, black liquor recovery boilers, biomassboilers, waste reclamation burners (trash burners), and the like.

Further steps may be taken to isolate the combustion conduit (or majorportion thereof) from chemical contamination and thermal stresses.

FIG. 6 shows an outlet/discharge end assembly 140 extending to an outlet30′. The outlet end assembly 140 may be used as a downstreamnozzle/outlet conduit section in place of the section 62 of FIG. 2.Although identified as a nozzle, this does not require the presence ofany particular convergence, divergence, or combination thereof in thenozzle. The exemplary assembly 140 provides means for thermally andchemically isolating upstream portions of the combustion conduit. Fromupstream to downstream, the assembly 140 includes a doubly flangedconduit segment 142 having upstream and downstream bolting flanges 144and 146. The body of the conduit segment 142 may have a number ofinstrumentation and/or sampling ports 148 which may be plugged to theextent not in use. The flange 144 has an upstream face for mounting tothe downstream face of the downstream flange of the penultimate conduitsegment. This junction may also serve for connection of the reactionstrap or other means. The flange 146 has a downstream face for matingwith the upstream face of an air curtain flange 150 which, as describedbelow, provides chemical isolation for portions of the combustionconduit upstream thereof. The air curtain flange 150 has a downstreamface for mating with the upstream face of a thermal isolation flange 152which is cooled to isolate upstream portions of the combustion conduitfrom heating (thermal soakback) from the furnace. The thermal isolationflange 152 has a downstream face for mating with an upstream face of aflange 154 of a nozzle assembly 156 having a nozzle body 158 extendingto the outlet 30′ and further cooled as described below. Nut and boltcombinations 160 extend through the bolt holes of the flanges 146, 150,152 and 154 to structurally and sealingly secure the assembly componentstogether.

The exemplary air curtain flange 150 (FIGS. 7 and 8) includes theupstream and downstream faces, an exterior perimeter surface 170 and aninterior surface 172 circumscribing the combustion gas flowpath. Anarray of bolt holes extend between the upstream and downstream faces.The interior surface 172 is at substantially even radius from thedetonation conduit centerline as is the interior surface of the adjacentconduit segment 142. An annular channel 174 is formed in one of thefaces (e.g., the downstream face) and is in communication via aconnecting passageway 176 with an exterior port 178 on the perimetersurface. An interior rim 180 (shown as a portion of the downstream faceseparated from the remainder by the channel) of the channel along theinterior surface is segmented or castellated by a circumferential arrayof slots 182. In the assembled condition, the mouth of the rim is closedby the adjacent face of its mating flange (e.g., the upstream face ofthe thermal isolation flange or the downstream face of downstream flange146 of the conduit segment 142). Gas (e.g., air, N₂, CO₂, or otherrelatively inert gas) may be introduced to the channel 174 through thepassageway and port (which may be provided with an appropriateconnection fitting (not shown in FIGS. 7 and 8)). When so introduced,the gas fills the channel and flows inward into the combustion conduitinterior through the slots. Exemplary air curtain flanges may bemachined (e.g., directly or from a casting or forging) of appropriatemetal (e.g., steel or nickel- or cobalt-based superalloy).

FIG. 16 shows an alternate thermal isolation flange 184 including achannel 185 and passageway 186. The alternate flange 184 may besimilarly constructed to the flange 150. The exemplary alternate flange184 differs in that its outlets are provided by full holes 188 in theinboard/interior surface rather than by recesses. Furthermore, thoseholes are angled so that the discharge outflow is off-radial (e.g., byan angle θ so as to have a downstream longitudinal component). The holecenterlines may, also, be oriented with a tangential component if atangential flow component is desired. The downstream longitudinal flowcomponent may further assist in preventing contaminant from passingupstream from the furnace. Exemplary values for θ are between 5° and60°.

In operation, the gas flow may supplement or replace a baselinecontinuous purge gas flow. The proximity of the air curtain flange 150to the outlet 30′ may provide improved resistance to the upstreamreinfiltration of combustion gases discharged from the apparatus andinfiltration of general furnace gases as well as particulatecontamination. In addition to contamination from particulates generatedwithin the furnace, the air curtain flow prevents accumulation ofparticulate reaction products from the combustion gases especially assuch gases may cool and precipitate out particles or liquid condensatewhich may, in turn, accommodate particle formation or sludge formation.If operated in a baseline fashion, the continuous gas flow may alsoprovide supplemental cooling of the conduit (especially downstream ofthe point of introduction).

FIGS. 9 and 10 show details of the exemplary thermal isolation flange152. The flange includes the upstream and downstream faces and anexterior perimeter surface 190. It further includes an interior surface192 encircling the combustion gas flowpath at substantially even radiusas the interior surfaces of the adjacent components. An array of boltholes extend between the upstream and downstream faces. A channel 194formed on one of the faces (e.g., the downstream face) extendslongitudinally inward therefrom. In the illustrated embodiment, thechannel has two general portions: a deep base portion 196 which is lessthan a full annulus; and a mouth portion 198 which extends to theassociated face and is a full annulus. The mouth portion is wider thanthe base portion extending both radially outward and radially inwardtherefrom to define a pair of annular shoulder surfaces 200 and 202. Inthe exemplary embodiment, the channel is machined in two steps. Themouth portion may be machined and then the base portion may be machinedbelow a base of the mouth portion, leaving a divider portion 204 of theflange between two ends of the base portion. Alternatively, the baseportion may initially be formed as a full annulus and then a separatedivider element inserted to turn the base channel into the partialannulus. A pair of passageways 206 and 208 connect the associated endportions of the channel base portion to associated exterior ports 210and 212 (e.g., in the flange perimeter surface). The exterior ports maybe equipped with appropriate fittings. In the exemplary embodiment, themouth portion of the channel accommodates a full annulus sealing ring214 which seats against the shoulder surfaces of the remaining bodypiece of the flange and may be welded in place to close the channel.Alternatively, in the absence of a mouth portion and sealing ring, theadjacent flange itself may close and seal the channel. In operation, aheat transfer fluid is introduced through one of the ports and withdrawnfrom the other after passing circumferentially through the channel.Exemplary heat transfer fluid may be liquid (e.g., aqueous (water or awater/glycol mixture) or oil-based) or gaseous (e.g., air orcompressed/refrigerated C0 ₂ or N₂) as may be appropriate for desiredheat transfer. Similarly, the heat transfer flowpath (e.g., channel)geometry and the flow rate may be tailored to achieve a desired heattransfer. The heat transfer fluid can both assist in cooling of thenozzle and in isolating elevated nozzle temperatures from upstreamcomponents. Such a thermal isolation flange may be used elsewhere in thesystem and may be used in other soot blower and different applicationswhere thermal isolation is required. Materials and manufacturingtechniques similar to those of the air curtain flange may be used.

FIGS. 11-14 show further details of the nozzle assembly 156. FIG. 13shows the nozzle assembly as including a main tube 220 having aninterior surface 222 and an exterior surface 224 and extending from anupstream rim 226 to a downstream rim 230 essentially defining the outlet30′. The interior surface may be at substantially even radius from thecenterline as interior surfaces of other components described above. Theflange 154 includes a main upstream piece 232 having upstream anddownstream faces 234 and 236, an interior surface 237, and an exteriorperipheral surface 238. The main piece 232 is secured to an upstreamportion of the main tube 220 with its interior surface contacting theexterior surface of the tube. Exemplary connection is by welding. Anannular plenum 240 may be machined in the main flange piece 232 (e.g.,as a rebate of an inboard portion of the downstream face). An outboardportion of the channel is closed by the second flange piece 242 havingupstream and downstream faces 244 and 246, an interior surface 248, andan exterior periphery 250. The upstream face 244 may abut the firstpiece downstream face 236 and be sealed thereto such as via an O-ring252 residing at least partially in a channel in one or both of thepieces. The two pieces may be held together by the same bolts/nuts 160or by separate bolts, welds, or the like. The interior surface 248 isspaced slightly apart from the tube exterior surface 224. A sleeve 254has interior and exterior surfaces 256 and 258 and extends from anupstream end/rim 260 to a downstream end/rim 262 (FIG. 13). The interiorsurface 256 is similarly spaced apart from the tube exterior surface 224and an upstream end portion is secured to the flange second piece (e.g.,accommodated in an annular rebate and welded thereto). A metering ring264 circumscribes the plenum 240 to separate radially inboard andoutboard portions thereof and has a plurality of apertures therein. Oneor more feed passageways 270 (two shown) are in communication with theplenum 240. The passageways 270 are in communication with ports (e.g.,in the flange first piece) 272 carrying fittings 274. A cooling fluid(e.g., a gas which may be similar to the air curtain gas) is introducedalong a nozzle cooling flowpath downstream through the fittings,passageways, and into the outboard portion of the plenum 240. The ring264 and its apertures meter the flow from the outboard portion of theplenum 240 to the inboard portion and help circumferentially distributethe flow when there are a relatively small number of discrete feedports. From the inboard/downstream portion of the plenum 240, the flowproceeds downstream in generally annular space 276 between the sleeve254 and tube 220. In the exemplary embodiment, the cooling gas flow isdischarged from a cooling gas outlet 278 between the sleeve downstreamrim 262 and the adjacent portion of the tube exterior surface 224. Inthe exemplary embodiment, the sleeve downstream rim is slightly recessedrelative to the tube downstream rim so as to mitigate the influence ofthe detonation wave on the cooling gas flow and mitigate the effect ofthe wave on the potentially relatively thin and fragile sleeve.

Advantageously, means are provided for maintaining the circumferentiallyspaced-apart relationship between the tube 220 and sleeve 254. Exemplarymeans include one or more spacer elements. The spacer elements may beassociated with means for measuring temperature parameters of the nozzlebody largely defined by the tube and sleeve downstream of the flange.FIG. 11 shows an exemplary first spacer 280. The exemplary first spaceris forked, having two tines 282 and 284 extending from upstream ends toa junction 286 from which a single leg 288 extends further downstream toa leg downstream end proximate the sleeve downstream end. The spacebetween the tines may accommodate an additional thermocouple (not shown)adjacent the junction and with its wires running back upstream andpassing through a thermocouple fitting port 290 in the main flange piece232. FIG. 15 shows a second spacer 292 as an elongate, nominallyrectangular, strip extending from an upstream end at the sleeve upstreamend to a downstream end at the tube downstream end 230. The exemplaryspacer 292 has, at its downstream end, an aperture between its outboardand inboard surfaces an aligned similar blind aperture extends inwardfrom the tube exterior surface. A thermocouple 294 is mounted within theblind aperture and has its body 296 extending outward, around thesleeve, and through a protective tube 298 (also FIG. 11) secured to theexterior surface of the sleeve. The thermocouple 294 serves to measuretemperatures at the tube downstream rim. Flange materials and mountingtechniques may be similar to those of the air curtain and thermalisolation flanges. Tube, sleeve, and ring materials may be similar andmay be made by a variety of known manufacturing techniques (e.g.,rolling and welding of sheet stock or machining).

In operation, the control and monitoring system uses the firstthermocouple 294 to principally monitor the temperature of the nozzleassembly portion exposed to the furnace interior. The aforementionedadditional thermocouple may be monitored as a back-up in the event of afailure of the first thermocouple when it is not desirable toimmediately initiate a shutdown for repair. The same or differentcritical temperatures may be utilized in determining shutdown based uponthe outputs of the two thermocouples.

Returning to FIG. 6, the nozzle assembly may be provided with aninterface plate 300 largely closing the portion of the furnace wallaperture outboard of the nozzle body. In operation, the plate 300 isnormally positioned in close or contacting proximity to the furnace wallouter surface. The plate may have a number of apertures foraccommodating various measuring, sampling, observation, and otherequipment. These apertures may be provided with covers when not in use.A series of struts 302 connect the plate 300 to the flange 154 to holdthe plate relative to the flange. The plate may have an aperture closelyencircling the body 158. The plate normally blocks the wall aperture toat least partially restrict flow of gases and particles from between thecombustion tube and wall aperture (e.g., inflow with a negative pressurefurnace). Upon discharge of the apparatus, the exemplary plate recoilswith the combustion conduit and is returned along therewith to itsoriginal place by the action of the reaction strap/spring combination.The exemplary plate material is steel or nickel—or cobalt-basedsuperalloy, optionally provided with an insulating layer (e.g.,cementaceous material).

One or more embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, the invention may be adapted for use with a variety ofindustrial equipment and with variety of soot blower technologies.Aspects of the existing equipment and technologies may influence aspectsof any particular implementation. Other shapes of combustion conduit(e.g., non-straight sections to navigate external or internal obstacles)may be possible. Accordingly, other embodiments are within the scope ofthe following claims.

1. An apparatus for directing a gas from an upstream conduit through avessel wall for cleaning surfaces within the vessel comprising: amounting flange for coupling the apparatus to the upstream conduitdelivering the gas and having: first and second faces; an inboardsurface bounding a central aperture; an outboard perimeter; and an arrayof bolt holes between the first and second faces; a conduit extendingdownstream from the flange and having: inner and outer walls along atleast a portion of a length; and a space between the inner and outerwalls for carrying a cooling fluid; a cooling fluid inlet; and a coolingfluid outlet.
 2. The apparatus of claim 1 wherein: the space extendsfrom an upstream end outside the vessel wall at least partiallydownstream within the wall.
 3. The apparatus of claim 1 wherein: thecooling fluid outlet is along the conduit; and the cooling fluid inletis along the flange.
 4. The apparatus of claim 3 wherein: the inner andouter walls each have a downstream rim; and the cooling fluid outlet isbetween the inner and outer walls.
 5. The apparatus of claim 1 wherein:the inner wall is essentially formed by a first tubular piece extendingfrom an upstream rim to a downstream rim and having interior andexterior surfaces, along an upstream portion, the interior surfaceproviding the flange inboard surface.
 6. The apparatus of claim 1 incombination with: said vessel, being a furnace, having a furnace wallseparating a furnace exterior from a furnace interior and having a wallaperture; and a detonative source of said gas.
 7. The combination ofclaim 6 wherein: the flange is upstream of an exterior surface of thefurnace wall; and the conduit extends through the furnace wall toprotrude downstream of an interior surface of the furnace wall.
 8. Asoot blower nozzle comprising: means for mounting the nozzle to anupstream soot blower gas conduit; a surface for guiding gas from thesoot blower gas conduit into the interior of the vessel; and means forcooling the nozzle.
 9. A method for operating an apparatus for cleaninginterior surfaces within a vessel having a vessel wall, the methodcomprising: causing a combustion pulse in a combustion conduit;directing combustion gases along the combustion conduit through thevessel wall to be ejected from an outlet of the combustion conduit; andpassing a cooling gas along a portion of the combustion conduit exposedto heat from the vessel.
 10. The method of claim 9 wherein: said passingis essentially continuous between a plurality of said combustion pulses.11. The method of claim 9 wherein: said passing comprises passing thecooling fluid along a path at least partially surrounding a portion of acombustion gas flowpath.
 12. The method of claim 9 wherein: said passingcomprises passing the cooling fluid along a path into the vesselinterior.